A “gene mutation” is considered to be any heritable change in the genetic code. Mutations are very rare events, on the order of one per million per cells per locus.
A number of gene-specific assays have been developed for measurement of human somatic mutations. Such assays provide a detection system that can detect and quantify rare mutations. These assays normally require access to a large quantity of cells and a reporter locus where mutations can be easily measured. One applied assay is the Glycophorin A (GPA) in vivo somatic mutation assay. See Chapter 9, section 9.2.3 of Methods to Assess DNA Damage and Repair: Interspecies Comparisons, edited by R. G. Tardiff et al., published by John Wiley & Sons Ltd, 1994.
A glycophorin is a sialoglycoprotein of the membrane of the red blood cell (also identified as RBC or erythrocyte). It is a membrane-spanning protein carrying sugar molecules; i.e. it is heavily glycosylated (˜60%). Glycophorins are rich in sialic acid, which gives the red blood cells a very hydrophilic-charged cell surface. This enables the cells to circulate without adhering to the vessel walls. Definition of “glycophorin” as obtained from Wikipedia on May 23, 2013, which is incorporated herein by reference.
Glycophorin A (also identified as GYPA or GPA) is the major and most abundant sialoglycoprotein of the erythrocyte membrane and bears the antigenic determinant for the MN blood group. The M and N antigens commonly occur in all populations. Definition and sequence listing of “glycophorin A” as obtained from the gene data base of the National Institute of Health (NIH) on May 23, 2013, which incorporated herein by reference.
The autosomal gene for Glycophorin A is located at the distal end of chromosome 4. This gene is the genetic determinant of the MN blood group. Two common alleles, M and N both present at frequencies ˜50% on red blood cells. The M and N forms of the Glycophorin A protein differ by two non-adjacent amino acids and are concomitantly expressed. See Chapter 9 section 9.2.3 of Methods to Assess DNA Damage and Repair: Interspecies Comparisons, edited by R. G. Tardiff et al., published by John Wiley & Sons Ltd, 1994, which is incorporated herein by reference. Monoclonal antibodies have been developed that distinguish between the allelic M and N forms of the Glycophorin A protein.